1. Field of the Invention
The invention relates to an apparatus for separating and drawing off a film laminated on a carrier material, having a base plate and a plate lying partly thereabove, at a distance.
2. Description of the Related Art
Light-sensitive layers or plies, such as for example exposed photoresist layers on circuit boards or color proof-films, are generally covered by protective films. In the production of color proof-films and printed circuit boards, a substrate is first coated with a light-sensitive material. The material is subsequently covered with a transparent film. This laminate of film and light-sensitive layer is then exposed image by image by a mask. This exposure effects an image-forming, differing adhesion of the photosensitive layer in such a way that the exposed parts adhere to the substrate with a stronger adhesion than the unexposed parts. When the protective film and the substrate are separated from each other, there is for example a positive image on the substrate and a negative image on the protective film.
In the production of circuit boards for electric circuits, the substrate is laminated with a light-sensitive dry resist film. The exposure of the dry resist film is performed with the aid of an imaging mask representing the electric circuit, and thereafter, the protective film is removed and the dry resist film is developed in various processing steps. The protective film on the dry resist film permits a largely dust-free exposure and the transport of the coated circuit boards in the stacked state. The circuit boards have specifically one or more borders which are free from the laminated-on protective film, so that the board can be grasped at these free borders by gripping tools or manually.
In the case of some laminating operations, it is desirable to completely transfer a coating from one surface to another surface, as is the case for example, when transferring a colored resin layer from a substrate to a receiving sheet. In such a case, the coated substrate and a receiving sheet laid thereupon are passed under pressure through a laminating nip of heated laminating rolls. The substrate and the receiving sheet are subsequently separated from each other and the colored resin layer is thereby transferred from the substrate to the receiving sheet. A problem in such transfer processes is the incompleteness of the transfer of the colored resin layer.
U.S. Pat. No. 4,752,346 describes an apparatus and a process for detaching and separating films adhesively bonded to one another. The apparatus comprises a platform of a metal or of a material of which the surface is provided with an electrically conductive layer. Over the surface there is a bar edge or a wedge. Both the bar edge and the platform surface are electrically grounded. The bar edge is positioned over the platform by means of supports at each end of the bar edge. The supports, which are surrounded by springs, are passed through the bar edge and protrude beyond it. Consequently, a variable gap can be formed between the underside of the bar edge and the surface of the platform, which makes it possible for laminates of different thicknesses, comprising substrate and film, to pass through the variable gap. For example, a colored photosensitive layer, which is covered by a receiving sheet, is applied to a transparent polyester film by means of an adhesive layer. This sandwich arrangement runs through the nip of laminating rolls and is subsequently introduced between the bar edge and the platform of the drawing-off apparatus. The transparent polyester film is drawn off over the bar edge by the film being bent upward over the edge angle and taken along the bevel of the bar edge. As a result, the polyester film is separated from the receiving sheet or the receiving film and a transfer of the adhesive layer and the colored photosensitive layer to the receiving sheet takes place.
German Offenlegungsschrift 3,443,939 discloses a process for removing the protective film from circuit boards laminated with exposed photoresist, with the aid of an adhering element in sheet form. The adhering element is adhesively attached to the protective film which is subsequently drawn off the circuit board substantially along its diagonal. In this case, the circuit board is adjusted by a turning apparatus in such a way that an angle of 0.degree.&lt;.alpha.&lt;90.degree. is set between the front edge of the board and the normal to the transporting direction. The front corner of the board is subsequently provided both on the upper side and on the underside with a double-sided adhesive adhering element in such a way that parts of the uncovered board, beyond the border of the protective film, are also grasped, and the protective film can be drawn off by means of rolls. The apparatus for carrying out the process comprises a transporting and adjusting device, by which the body in board form can be swivelled out of its transporting direction into a working position. Furthermore, the apparatus includes a device for applying a double-sided adhesive adhering element, which is designed in the form of tongs and has bodies in plate form for receiving bearing rollers, and a device for removing the adhering element and the protective film, bonded to the latter, of the body in board form. This apparatus has a system of rolls arranged axially parallel, with a device for keeping the distance between the rolls constant.
German offenlegungsschrift 3,339,723 discloses a process and an apparatus for detaching the protective film from laminated circuit boards, in which the laminated circuit boards run via transport rollers and are provided on their upper side and underside with a one-sided glued adhesive tape. The protective film is detached by a subsequent drawing-off of the applied adhesive tape over a bar edge and is subsequently transported away and stored. The bar edge and the circuit board form a drawing-off gap through which the circuit boards pass. The bar edge forms an angle of 45.degree. with respect to the transporting apparatus, and the adjoining face likewise forms an angle of 45.degree. with respect to the board plane.
In the case of the known apparatuses for detaching a protective film from a laminated circuit board, either a continuous or endless adhesive tape or individual, double-sided adhesive elements are used, a result of which is that additional material and considerable amounts of such material are required. Furthermore, further process steps are required in advance, in order to bring either the adhesive tape or the adhesive elements onto the protective film of the circuit board.